Alkylation of isoparaffins with isomerized olefins



A *WA IYM.

Patented Apr. l, 1952 ALKYLATIon F ISOPARAFFINS WITH .ISOMERIZED OLEFINS Sumner H. McAllister, Lafayette, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application July 21, 1945, Serial No. 606,475

9 Claims. (01. 260-6834) This invention relates to the manufacture of motor fuel and deals particularly with a new and more efficient method of producing products of improved anti-knock value by alkylating isoparaffins with olefins.

Great advances have been made in the pro duction of high octane gasoline within recent years, particularly as a result of the large scale adoption of isoparafiin alkylation. In the alkylaction of isoparaflins to produce gasoline components, a wide variety of olefins have been sug gested, but the olefins produced by the thermal or catalytic cracking of higher boiling hydrocarbons have been used almost exclusively. These olefins aremade up of mixtures of straight and branched chain compounds which have the double bond at different locations in the chain. It has been proposed to segregate these olefins into fractions composed predominantly of olefins having the same number of carbon atoms per molecule and to alkylate isoparafins with the separated fractions, which, in the case of fractions having olefins of more than three carbon atoms, are still mixtures comprising branched chain tertiary olefins with secondary olefins having the double bond at the end of the chain as well as removed therefrom, e. g. secondary l-olefins, 2-olefins, etc.

In some .cases the tertiary olefin content of such mixtures has been selectively removed prior to alkylation with the remaining secondary olefins. However, it has always been considered heretofore that all olefins having the same number of carbon atoms per molecule were substantially equivalent as isoparaflin alkylating agents, and it has been the practice to use olefinic mixtures containing both 'l-olefins and 2-olefins as the alkylation feed stock.

It has now been found that superior results maybe obtained in the catalytic alkylation of isoparaffins by using olefins having the double bond removed from the end of the chain as the alkylating agent. Typical examples of such more advantageous olefins are, for example, the 2-oleflns such as Z-butylene, 2-amylene, Z-methyl butene-Z, 2-hexylene, and the like. The secondary 2-o1efins are preferred alkylating agents in the process of the invention, but olefins having the double bond further removed from the end of the chain, as in 3-hexylene, Z-methyl hexene-3, etc., may also be used. In one specific embodiment the process of the invention comprises isomerization of a secondary l-olefin to a 2-olefin using any suitable isomerization catalyst; and .alkylating an isoparaffin, preferably a low boiling isoparaffin such as isobuta'ne and/or isopentane, with the resulting 2-olefin in the presence of an alkylation catalyst. By the method of the invention not only may the yield and quality of the alkylate be increased but also the effective life of the alkylation catalyst may be extended, thus reducing the cost of alkylation, compared to the results obtainable by alkylation of the isoparaifin With the original l-olefin.

A number of different methods are available for carrying out the isomerization of secondary l-olefins to 2-olefins. U. S. Patent 2,379,731, for example, describes a particularly suitable method using sulfuric acid as the catalyst. Other catalysts include alumina, preferably acidtreated, eqg. by soaking in 1 normal hydrochloric acid and then drying, zinc chloride, silica or silica-alumina gels, alkaline earth oxides, preferably calcined, Superfiltrol, oxides of titanium, beryllium, zirconium, chromium and the like, etc. With solid granular catalysts such as these, the isomerization may be carried out, for example, by passing the l-olefin or the 1- olefins in the gaseous state through tubes or towers packed with the catalyst. Preferably, however, the feed stock is maintained at least partly in the liquid phase and most advantageously the reaction is carried out under conditions such that the desired isomerization product is continuously separated from the unreacted l-olefin and removed from the reaction zone substantially as fast as formed, leaving the l-olefin therein for further reaction. One method of achieving this end is by use of a distillation column containing the solid isomerization catalyst. The l-olefin-containing feed may be supplied in the liquid phase to the top of the column and is isomerized as it flows downward through the catalyst, the feed rate and temperature being preferably regulated so that the olefinic mixture corresponds substantially to the equilibrium mixture for the existing tempera ture when the hydrocarbons have traversed the catalyst bed. The product then passes into a fractionating zone (free from catalyst) which may be a part of the same column or a separate unit. In either case the unreacted l-olefin is returned to the catalyst zone for further reaction. Where the fractionator is the lower part of the reaction column, the separated lolefin may pass directly up the catalyst column as vapor in countercurrent to the descending '2- olefin since, at least among the lower olefins, the l-lsomers boil sufliciently below the boiling point of the desired 2-olefins to make this method of operation feasible. However, particularly when using a separate distillation column, it is generally more satisfactory to return the separated unreacted l-olefin to the reaction with the feed.

The isomerization may be carried out equally satisfactorily by means of catalysts which need not be solids. Not only the previously mentioned sulfuric acid but also the other acids such, for example, as phosphoric acid, benzene sulfonic acid, hydrogen fluoride, perchloric acid, etc., may be used in the liquidstate. However, even these acid catalysts may, if desired, be used as deposits or coatings on carriers such as clay, alu mina, silica or other suitable solid materials. The previously discussed solid isomerization catalysts may be similarly used in order to increase their effective surface.

The temperature, pressure and feed rate are adjusted with respect to the particular olefin or olefins involved and the activity of the isomerization catalysts chosen so as to given the desired conversion with minimum side reactions; Thus, temperatures in the general range of about 38 C. to about 425 C. are suitable, the time of contact being preferably reduced as the temperature is increased. Polymerization and/or other side reactions during isomerization with acid catalysts may be reducedby using these catalysts in the form of aqueous solutions; thus, hydrogen fluoride of about to 80%, preferably about concentration, or sulfuric acid of about to 90%, preferably about strength, may be used. It is even feasible to carry out the olefin isomerization non-catalytic'a-lly, but temperatures of the order of about 600 C. or higher are generally required and these lead to substantial side reactions which make such methods less desirable. The isomeri'zation may be effected under conditions at which rearrangement of the carbon structure takes place in addition to the desired shift in the double bond, but this is not objectionable, and may even be advantageous in some cases, as long as the isomerization product is an olefin having the double bond removed from the end of the chain. Catalysts such as boric oxide on alumina, zeolites, etc. may be used for this type ofisomerization.

As previously pointed out, the usual sources of olefins' of four or more carbon atoms per molecule aregenerally mixtures containing both terminally unsaturated secondary olefins and secondary olefins havingthe double bond further removed from the end of the chain as well as tertiary olefins and diolefins. With such starting materials, it is desirable to separate diolefin and tertiary monoolefihs from the secondary olefins before carrying out'the isomerization of the alpha olefin content. Selective polymerization or hydrogenation or reaction with maleic anhydride may be used for the removal of diolefins. The tertiary olefins may be removed by extraction, for example, with sulfuric acid as described in U. S. Patent 2,007,159, or' by selective polymerization, for instance, as

. claimed inU. S. Patent 2,007,160, or by other suitthe secondary olefin-containing mixture may be distilled to separate a fraction containing the terminally unsaturated olefin from olefins having the double bond removed from the end of the chain. Such distillation may advantageously be carried out in the same unit as is used for the fractionation of the isomerization product. Where the product fractionation unit is an inte gral part of the isomerization reactor as pre viously described, the'feed mixture containing 1- olefin and 2-olefin may be introduced at a point below the catalyst zone and the separated l-olefin vapors will pass up the tower and be isomerized isomerization product.

then fed, according to the invention, to the alkylation system for reaction with a paraffin such as isobutane, isopentane, or the like. Acid catalysts, such as sulfuric acid of about to concentration, hydrogen fluoride which may be anhydrous or aqueous, phosphoric acid, chlorosulionic or fluorosulfonic acids, hydrofluoroboric 'acid, etc, may be advantageously used in the process. Instead of the individual catalyst acids, not only may mixtures of such acids be employed but also mixtures of one or more such catalysts with other materials having a beneficial effect on the reaction, for example, boron fluoride, phosphorus pentoxide, oxides of vanadium, zinc or cadmium phosphates, sulfur dioxide and/or trioxide, may be used. Another suitable group of alkylation catalysts are the metal halides, parparafiins, maybe used directly as feed" to the previously described isonierization. Alternatively,

ticularly the Friedel-Crafts'type catalysts. Aluminuin chloride, aluminum bromide, ferric chloride, titanium tetrachloride and antimony trichloride have been found to be suitable; Less ac- I tive catalysts such as stannous or stannic chloride, bismuth chloride, etc. may also be used The catalysts may be used in solid form as lumps or granules, or finely divided powders, or'rnay be deposited on supports or carriers which may be inert or may have an advantageous influence on the reaction. U. S. Patent 2,295,977, for example, describes a methodsuitable for. the preparation of such supported catalysts. Catalysts inthe liquid state offer many advantages in the process. Friedel-Crafts type catalysts such as the aluminum halides may be used in this formsby converting them to organic complexes. Organic complexes of active metal halides and ketones such as described in U. S. Patent 2,085,535,. or metal halide-alkyl halide complexes such asmay be prepared, for example, by refluxing. the tertiary alkyl halide to be used in the reaction with the corresponding aluminum. halides, may be used. Other suitable complex catalysts are those formed by the union of active metal halides with hydrocarbons, which maybe'either aliphatic. or aromatic, or mixtures of; hydrocarbons. The catalysts claimed in U. S. Patent 2,306,261, for example, may be used; Double salts-of aluminum chloride such' as are described in' U. S. Patent 2,076,20l'are also useful in the process; C'omplexes or sludges formed in the course of the reaction may, after addition of fresh metal halide, be used as the catalyst' While boron fluoride may be used as a gas, it is likewise. preferable in liquid form. With Friedel-Crafts type catalysts, it is usually advantageous to use a small amount of an activator such as the corresponding hydrogen halide or the like.

Any suitable method of reacting paraffins with the Z-olefins in the presence of alkylation catalysts may be used in the alkylation step of the process. The alkylation may be carried out with either or both reactants in the vapor phase, but liquid phase reaction is preferred. Any suitable method of intimately mixing the reactants and catalyst acid'may be employed. For example, jet mixers, towers provided with suitable baffles 01' packing, power-driven mixers and the like may be used. For large scale, continuous operation mixing by means of a pump which is in communioation with a separator wherein reaction prod- -ucts'may'be separated at least in part from catalyst acid and the latter returned to the reaction, preferably together with a part of the separated product-containing phase to which fresh reactants are added before being contacted with catalyst acid, is advantageous. A preferred method of operation which is more fully described and claimed in U. S. Patent 2,232,674 comprises circulation of a stream of reacted mixture containing unreacted isoparafin and continuously feeddesirable in any particular case will depend upon the nature of the isoparaffin and olefin involved. Where sulfuric acid is employed as the catalyst, initial concentrations of about 90% to 100% may be used although fuming H2804 is also suitable provided lower reaction temperatures are used.

Temperatures of the order of about 5 C. to 50 C. may be used. The proportion of catalyst to hydrocarbon which will be desirable will depend upon the olefin being reacted. In general, volume ratios of about .5:1.0 to about 4:1 are suit able. Reaction times of about five to thirty-five minutes are preferred but may be varied depending upon the type of apparatus and method of operation from a fraction of a minute to as much as sixty minutes. Most preferably molar ratios of isoparafiin to olefin of at least 20:1 are used in the reaction mixture in order to favor alkylation and to suppress undesirable reactions such as olefin polymerization, and it is usually advantageous to use ratios of the order of 50:1 to 500:1 at the point where the olefin first contacts the acid. While the same ratio of parafiin to olefin may be used in the feed as is employed in the reaction, when the preferred method of feeding reaction mixture into recirculated reaction product is used, ratios of isoparafiin to olefin of about 3:1 to 20:1 in the feed are preferred. Single or multiple stage alkylation with either concurrent or countercurrent fiow of reactants and catalyst may be used with either batchwise, intermittent or continuous operation.

Whatever the method of alkylation adopted, the hydrocarbon phase of reaction products may be treated to separate the alkylate from the excess un-reacted isoparafiln and the latter returned to the reaction. Where volatile catalysts are used, any small amount remaining in the reaction product after separation of the bulk of the catalyst, as previously described, may be recovered and returned to the reaction with the excess isoparaflln.

The following examples show specific applications of the process of the invention and illustrate certain of its advantages:

Example I To show the superiority of the 2-olefins over the corresponding l-olefins, alphaand betabutylenes were separately alkylated under the following conditions, with the results shown'below:

10 mols isobutane per mol olefin in the feed 87 70-89% isobutanein the feed Y 100% H2804 as catalyst 10 C. alkylation temperature 1 vol. acid per vol. of hydrocarbon 20 min. contact time Butylenes Alpha Beta Acid life 1o 15 Light alkylate (15 C.i50 O.) in product percent. 96-97 97-98 Percent octanes in product do 93 05 ASTM, ON of product in 95%97% acidity range 90. 0 97. 2 Light ends pcrcent 3. 5 2. 5

Example 11 Untreated Isomerizcd Feed Feed Composition of feed:

Propane-propylene. O. 4

Isobutylene 5. 1 0. 1

i-Butylene 4. 4 1. 5

2'Butylene. 4. 9 l0. 2

lsobutane. 71. 5 53. 4

N-butzme l3. 7 34. 8 Quality of Product:

Octane number of aikylatc 92. 5 93. 7

It will be apparent from this description of the invention that it offers many advantages over prior methods of operation. Not only does the process give more uniform results because the olefins are more uniform but also longer catalyst life in the alkylation, and alkylation products of improved quality are obtained because the isomerized olefins are predominantly beta-olefins.

Many variations may be made in the process, the various steps of which may be carried out batch-wise or intermittently instead of continuously. Still other variations may be made not only in the materials treated, but also in the details of operationemployed, and it will be understood that the invention is not limited to the procedure disclosed by way of example, nor by any theory suggested in explanation of the improved result obtained.

This application is a continuation-in-part of application Serial No. 428,656, filed January 29, 1942, and which issued as Patent No. 2,460,303 on February 1, 1949.

v 7 I claim as my invention: 1. A process of producing higher boiling hydrocarbons which comprises treating hydrocarbon of the same number of carbon atoms per molemile, and contacting a mixture of said resulting beta-olefin and a substantial molar excess of an isoparaffin with an alkylation catalyst under alkylating conditions.

3. A process for producing high octane parafiins from an isoparafiin and secondary olefins, each having four to five carbon atoms per molecule,

owhich comprises isomerizing a mixture of said olefinst under conditions eifecting conversion of l-olefins to z-olefins, admixing the effluent of said isomer-ization with the isoparaflin, and contacting the resulting mixture with an alkylation catalyst under conditions effecting alkylation' of the isoparafiin with said 2-olefin.

4. The improved process of producing high octane parafiins from an isoparaffin and a secondary l-olefin, each having four to fivecarbon atoms per molecule, which comprises subjecting said l-olefin to the isomerizing action of a cataly t capable of isomerizing said l-ole'fin to the corresponding 2-o1efin, and alkylating said isoparafiin with the resulting isomerization efiluent inthe presence of an allgylation catalyst.

5. The improved process of producing high octane, motor fuel parafiins fr m an i op ra fin and a secondary l-o efin. a h havin e to 11V? carbon atoms per molecule, which comprises subjecting said l-olefin to the isomerizing action of a catalyst capable of isomerizing said l-olefin to the corresponding 2,-o1efin, alkylating said isoparaffin with the resulting isomerization eiiluent in the presence of concentrated sulfuric acid and isolating from the resulting alkylation mixture a motor fuel of high octane rating.

6. The process of claim 5, in which said isoparafiin is isobutane.

7. The process .of claim 5, in which said l-oleiin is butenev-l. v o 8. A process of producing higher boiling hydrocarbons, which comprisestreating hydrocarnon containing alpha-buiy ene nder condition at which said olefin is isomerizedto bcta-butitlene and contacting a mixture of the resulting beta butylene and a substantial molar-excess of isobutane with sulfuric acid under 'alk y l'ating con, ditions.

9. A process of producing high octane motor fuel paraffins which comprises contactin alphabutylene with sulfuric acid under conditions at which said olefin is 'isomerized to betabutylene and contacting a mixture of the resultingfbetafbutylene and a substantial molar excess'of isolbutane with an alkylation catalyst under alkyllating conditions. 7 k

V SUMNER MCALLISTERL REFERENCES CITED.

The following references are of record in the file of t is pa n UNITED STATES PATENTS Number Name. Date 2,18Q,3 7j4 Stahley et a1. Nov. 21,1939 2,260,945. Korpi et a1, Oct. 28;."l9'41 2,327,926 Oakley et. a1 V Aug. 2.4, 1:943 

1. A PROCESS OF PRODUCING HIGHER BOILING HYDROCARBONS WHICH COMPRISES TREATING HYDROCARBON CONTAINING AN ALPHA-OLEFIN OF AT LEAST FOUR CARBON ATOMS PER MOLECULE UNDER CONDITIONS AT WHICH SAID OLEFIN IS ISOMERIZED TO AN OLEFIN OF THE SAME NUMBER OF CARBON ATOMS PER MOLECULE BUT HAVING A MORE CENTRALLY LOCATED DOUBLE BOND, AND ALKYLATING AN ISOPARAFFIN WITH THE RESULTING ISOMERIZED OLEFIN IN THE PRESENCE OF AN ALKYLATION CATALYST. 